linux-kernel - Re: [RFC PATCH 1/6] ACPI: Introduce ACPI D3

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Message-ID: <1329203228.19384.35.camel@rui.sh.intel.com>
Date:	Tue, 14 Feb 2012 15:07:08 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Lin Ming <ming.m.lin@...el.com>, Jeff Garzik <jgarzik@...ox.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Tejun Heo <tj@...nel.org>, Len Brown <lenb@...nel.org>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>
Subject: Re: [RFC PATCH 1/6] ACPI: Introduce ACPI D3_COLD state support

Hi, Rafael,

On 一, 2012-02-13 at 21:25 +0100, Rafael J. Wysocki wrote:
> On Monday, February 13, 2012, Lin Ming wrote:
> > From: Zhang Rui <rui.zhang@...el.com>
> > 
> > If a device has _PR3._ON, it means the device supports D3_HOT.
> > If a device has _PR3._OFF, it means the device supports D3_COLD.
> > Add the ability to validate and enter D3_COLD state in ACPI.
> > 
> > Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> 
> This is supposed to be ACPI 5.0 support, right?
> 
No, D3_HOT is introduced in ACPI spec 4.0.
According to the spec, _PR3 is used for devices that support both
D3(D3_COLD) and D3HOT.

The confusion here is that Linux D3 equals ACPICA D3HOT and Linux
D3_COLD equals ACPICA D3.
For example, when enter Linux ACPI D3, the reference count of ACPI Power
Resources in _PR3 is increased by one.

> So can anyone please tell me what part of the ACPI 5.0 spec is the
> basis of this patch, because I can't see that immediately?
> 
> The only places where D3Cold is _mentioned_ are Section 7.2.12 (_PRE, which
> appears to be new in 5.0), Section 7.2.20 (_S0W), Section 7.2.21 (_S1W),
> Section 7.2.22 (_S2W), Section 7.2.23 (_S3W) and Section 7.2.24 (_S4W).
> None of them mentions those _PR3._ON and _PR3._OFF things above.
> 
> Moreover, my understanding of the spec is that D3Cold means all of the
> power resources returned by _PR3 are "off" (whereas some of them will be
> "on" in D3hot).
> 
Agreed.

> > ---
> >  drivers/acpi/power.c |    4 ++--
> >  drivers/acpi/scan.c  |   10 +++++++++-
> >  2 files changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
> > index 9ac2a9f..0d681fb 100644
> > --- a/drivers/acpi/power.c
> > +++ b/drivers/acpi/power.c
> > @@ -500,14 +500,14 @@ int acpi_power_transition(struct acpi_device *device, int state)
> >  {
> >  	int result;
> >  
> > -	if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3))
> > +	if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3_COLD))
> >  		return -EINVAL;
> >  
> >  	if (device->power.state == state)
> >  		return 0;
> >  
> >  	if ((device->power.state < ACPI_STATE_D0)
> > -	    || (device->power.state > ACPI_STATE_D3))
> > +	    || (device->power.state > ACPI_STATE_D3_COLD))
> >  		return -ENODEV;
> >  
> >  	/* TBD: Resources must be ordered. */
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index 8ab80ba..a9d4391 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -881,8 +881,16 @@ static int acpi_bus_get_power_flags(struct acpi_device *device)
> >  
> >  			device->power.flags.power_resources = 1;
> >  			ps->flags.valid = 1;
> > -			for (j = 0; j < ps->resources.count; j++)
> > +			for (j = 0; j < ps->resources.count; j++) {
> >  				acpi_bus_add_power_resource(ps->resources.handles[j]);
> > +				/* Check for D3_COLD support. _PR3._OFF equals D3_COLD ? */
> > +				if (i == ACPI_STATE_D3) {
> > +					if (j == 0)
> > +						device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
> > +					status = acpi_get_handle(ps->resources.handles[j], "_OFF",  &handle);
> > +					device->power.states[ACPI_STATE_D3_COLD].flags.valid &= ACPI_SUCCESS(status);
> > +				}
> > +			}
> 
> Sorry, but this doesn't make sense to me.  Power resources always have
> the _OFF method, right?
> 
I'm not sure. I thought I had seen ACPI Power Resources without _OFF
control method somewhere in bugzilla, but I can not find it out now.

Hmm, how about set D3_COLD support if _PR3 exists, but leave a warning
message if _OFF doesn't exist, for now?

thanks,
rui


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